1. Field of the Invention
The present invention relates generally to apparatus and methods for detecting analytes in liquid samples. More particularly, the present invention relates to an analytical system and method for dispensing liquid samples and reagents into an analytical rotor, manipulating the rotor to perform a desired assay, and detecting assay results within the rotor.
Several automated analytical systems have been developed for the detection and measurement of biological and other analytes in liquid samples. While such systems can be classified in many ways, the present invention is particularly concerned with assays which use analytical rotors for performing some or all of the steps necessary for a desired testing protocol. Assay protocols which use rotors generally rely on introduction of a liquid sample to the rotor followed by spinning of the rotor to transfer the liquid sample and optionally other liquid reagents between various reaction and detection chambers in the rotor. Rotation and/or back and forth motion of the rotor often is also relied on to mix the liquid sample with diluents, other reagents, and the like. The use of analytical rotors is advantageous since they provide a self-contained platform for performing the desired analytical method. Moreover, the use of analytical rotors is often relied upon for separating cellular components from whole blood to produce plasma suitable for testing.
Heretofore, analytical rotors have been most widely used for performing enzymatic and other non-immunological testing procedures. Such non-immunological test protocols often do not require multiple, sequential reaction steps where different reagent solutions will be passed successively past a solid phase surface where the immunological reaction(s) occur. That is, most enzymatic tests can be run in a single chamber or cuvette by providing appropriate lyophilized or other dried reagents within the chamber. It is then only necessary to introduce a desired volume of plasma or other liquid sample, where a resulting enzymatic reaction produces a detectable color signal. Thus, most instruments for handling rotors do not require substantial liquid handling and other capabilities for performing multiple, sequential addition of sample and reagent(s) to a reaction chamber within the rotor.
For these reasons, it would be desirable to provide an improved system and methods for the manipulation and handling of analytical rotors to perform immunological assays. In particular, it would be desirable to provide instruments which are able to position the rotor successively at different locations and/or orientations to receive sample and other liquid reagent(s) in a preselected order and amount. The instrument and method should preferably be able to transfer the rotor between different operative locations within the instrument, while at all times retaining the ability to spin the rotor at desired rotational speed(s) in order to effect fluid transfer within the rotor in a manner consistent with the test protocol. The instrument should have the ability to receive fresh containers of diluent and optionally other liquid reagents and to further dispense such liquids to the rotor at appropriate points within a test protocol. The instrument should further include the ability to dispense liquid sample to the rotor, preferably having the ability to separate and dispense plasma from a whole blood sample supplied to the instrument in the self-contained receptacle. Furthermore, the instrument should have an integral signal detector capable of reading signal directly from the rotor, such as a fluorescent signal which is produced by exposing the rotor to an appropriate excitation source. The system and method of the present invention will meet at least some of the above objectives.
2. Description of the Background Art
U.S. Pat. No. 4,314,968, describes an analytical rotor intended for performing immunoassays. Analytical rotors intended for separating cellular components from whole blood samples and distributing plasma to one or more peripheral cuvettes are described in U.S. Pat. Nos. 3,864,089; 3,899,296; 3,901,658; 4,740,472; 4,788,154; 5,186,844; and 5,242,606. Analytical rotors intended for receiving sample liquids and transferring the samples radially outward by rotation of the rotor, usually with dilution of the sample, are described in U.S. Pat. Nos. 3,873,217; 4,225,558; 4,279,862; 4,284,602; 4,876,203; and 4,894,204.